Module
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The Basics and Beyond:
An Introduction to Heredity
A Tree of Genetic Traits
Abstract
Students mark their traits for tongue rolling, PTC
tasting (a harmless, bitter chemical), and earlobe
attachment on tree leaf cut-outs. They then place
their leaves on a large tree whose branches each
represent a different combination of traits. When
completed, the tree forms a visual representation of
the frequency of trait combinations within the class.
Time Required
An individual will have many
traits they share in common
with others.
Some traits are more common
in a population than others.
Class Time:
30 minutes
Prep Time:
30 minutes to review activity, make copies
of tree leaf cut-outs, and prepare traits tree
Materials
PTC paper, hard candies, leaf cut-outs, large
butcher paper, tape, scissors
Prior Knowledge Needed
Appropriate For:
Traits are observable
characteristics that are passed
down from parent to child.
An individual’s overall
combination of traits makes
them unique.
Logistics
None
Learning Objectives
Special Features
You’ll Find Inside
A sample Genetic Traits Tree
to demonstrate the shape and
labeling for your class drawing.
And, how to access a readymade, large traits tree that can
be printed at your local copy
store.
Ages: 10 - 13
USA grades: 5 - 7
© 2006 University of Utah
This activity was downloaded from: http://learn.genetics.utah.edu/teachers
Print-and-Go™
Module
The Basics and Beyond:
An Introduction to Heredity
http://learn.genetics.utah.edu
A Tree of Genetic Traits
Classroom Implementation
Quantities
Activity Instructions:
• Draw a large tree, several feet tall, on butcher paper (see page S-2 for
a suggested tree shape and labels). Post the Genetic Traits Tree in an
easily accessible and visible area of the room. Provide each student a
leaf and instruct them to cut it out.
Per Student
One leaf cut-out, hard candy
Per Group of 2
• Explain that traits are observable characteristics we inherit from our
PTC paper, scissors, tape
parents. Demonstrate the tongue rolling and earlobe attachment traits.
Have students mark “yes” or “no” on their leaf for these traits as appropriate.
• Hand out PTC paper. Instruct students to place a piece of PTC paper on the tip of their tongue to see if they
can taste anything. The chemical tastes bitter to those who can taste it. For those who cannot taste PTC,
the paper has no taste.
• Note: PTC paper is inexpensive and can be purchased from Sargent Welch (www.sargentwelch.com), Carolina
Math and Science (www.carolina.com) or Ward’s Natural Science (http://www.wardsci.com).
• Instruct students to check “yes” or “no” on their leaves for PTC tasting. Hand out a hard candy to each
student to neutralize the taste of the PTC.
• Demonstrate how to determine where to place the leaves on the Trait Tree starting at the base of the
branches and working your way out toward the tips.
• Call students up in groups to place their leaves on the appropriate branches. The leaves will be clustered
around the branch representing the most common
combination of traits in the class. Some branches of the
tree will remain relatively sparse.
• Optional: Make leaf cut-outs in two different colors, one for
boys and one for girls, to track combinations of traits within
the different genders.
• Optional: Increase your data pool by including other classes
in the exercise, taping all leaves to one tree.
Discussion Points:
Common Misconceptions
A widespread misconception is that all traits
exhibit either a dominant or recessive pattern of
inheritance. But these terms only apply to single
gene traits. The traits included in this activity are
part of the small number that may be due to only
one or two genes. However, most human genetic
traits are influenced by several genes as well as
interactions with the environment. The inheritance
of complex traits is difficult to predict, and does
not follow typical dominant or recessive patterns.
• Some traits are more common in a population than others.
What is the most common combination of traits in the class? What is the least common combination of traits
in the class? How does this compare to the most and least common individual traits in the class?
• Every person has a unique combination of traits. If we were to look at more traits than three, we would
eventually need a branch on the Trait Tree for each person in the class.
© 2006 University of Utah
This activity was downloaded from: http://learn.genetics.utah.edu/teachers
1
Print-and-Go™
Module
The Basics and Beyond:
An Introduction to Heredity
http://learn.genetics.utah.edu
A Tree of Genetic Traits
Standards
U.S. National Science Education Standards
Grades 5-8:
Content Standard C: Life Science - Reproduction and Heredity
• Every organism requires a set of instructions for specifying its traits. Heredity is the passage of these
instructions from one generation to another.
• The characteristics of an organism can be described in terms of a combination of traits.
AAAS Benchmarks for Science Literacy
Grades 3-5:
The Living Environment: Heredity - Some likenesses between children and parents, such as eye color in human
beings, or fruit or flower color in plants, are inherited. Other likenesses, such as people’s table manners or
carpentry skills, are learned.
For offspring to resemble their parents, there must be a reliable way to transfer information from one
generation to the next.
Additional Resources
Credits
Activity created by:
Molly Malone, Genetic Science Learning Center
April Mitchell, Genetic Science Learning Center
Harmony Starr, Genetic Science Learning Center
(illustrations)
This activity was adapted from “State Your Traits
- Genetic Traits Tree”, The GENETICS Project,
University of Washington (2001).
Visit the Learn.Genetics website to get links to great
resources like these! Just log-in as a teacher and
click on The Basics and Beyond.
• Tour of the Basics: An animated tutorial that contains
background information on DNA, genes, patterns of
inheritance and more!
• Inherited Human Traits: A Quick Reference: A pictorial
reference and description of inheritance, and inheritance
patterns (dominant, recessive, sex-linked, polygenic) for
several human traits, including those described in this
activity.
• Genetic Traits Tree: A ready-made, large traits tree that
can be downloaded and printed at your local copy store.
© 2006 University of Utah
This activity was downloaded from: http://learn.genetics.utah.edu/teachers
2
Print-and-Go™
Module
The Basics and Beyond:
An Introduction to Heredity
http://learn.genetics.utah.edu
A Tree of Genetic Traits
Adapted from “State Your Traits - Genetic Traits Tree”, the GENETICS Project, University of Washington (2001).
Leaf Cut-outs
Earlobes
Attached
Earlobes
Attached
Free
PTC Tasting
Yes
PTC Tasting
No
Yes
Yes
No
Yes
Earlobes
Attached
Free
PTC Tasting
Yes
Yes
Earlobes
Attached
PTC Tasting
Yes
No
Free
PTC Tasting
Yes
No
Tongue Rolling
© 2006 University of Utah
Tongue Rolling
Earlobes
Attached
PTC Tasting
Yes
No
No
Free
Yes
Free
Yes
Tongue Rolling
Earlobes
Attached
No
PTC Tasting
No
Yes
No
Tongue Rolling
No
Free
Yes
Free
Yes
Tongue Rolling
Earlobes
Attached
No
PTC Tasting
No
Yes
No
Tongue Rolling
Tongue Rolling
Earlobes
Attached
Free
No
No
Tongue Rolling
Yes
This activity was downloaded from: http://learn.genetics.utah.edu/teachers
No
3
Print-and-Go™
Module
The Basics and Beyond:
An Introduction to Heredity
http://learn.genetics.utah.edu
A Tree of Genetic Traits
Adapted from “State Your Traits - Genetic Traits Tree”, the GENETICS Project, University of Washington (2001).
Example Trait Tree
Tongue
Roller
Non-Tongue
Roller
Tongue
Roller
Non-Tongue
Roller
Non-Tongue
Roller
Tongue
Roller
© 2006 University of Utah
PTC
Taster
Non-PTC
Taster
Attached
Earlobes
PTC
Taster
Tongue
Roller
Non-PTC
Taster
Free
Earlobes
This activity was downloaded from: http://learn.genetics.utah.edu/teachers
Non-Tongue
Roller
4